Polymeric material containing 1, 2-dicyano-1-methylethylene



Patented Aug. 24, 1948 POLYMERIC MATERIAL CONTAINING 1,2-DICYANO-1-MI'ITHYLE'I'HYI'J'INE David '1'. Mowry, mm, Ohio, assignor toMonsanto Chemical Com notation oi Delaware Dani, St. Louis, 110., a cor-No Drawing. 7 Application July 24, 1944,

Serial No. 546,433

4 Claims. (01. 260-485) The present invention relates to the productionof resinous material by the copolymerization 01' vinyl aromatichydrocarbons and 1,2-dicyanol-methylethylene, (1,2-dicyano-1-propylene)An object of .the present. invention is to provide resinouscopolymerization products of CHzrC substituted aromatic hydrocarbonssuch as styrene, alpha-methylstyrene and alpha.para- 'dimethyistyrene,together with 1,2-dicyano-1- methylethylene, which products haveimproved physical strength characteristics as well as a higher thermalstability (heat distortion point) than does the polymerized vinylaromatic hydrocarbon itself.

I have found that valuable interpolymerization products may be obtainedby polymerizing a mixture containing 1,2-dicyano-1-methylethylene and aCH2=C substituted aromatic hydrocarbon such as styrene,alpha-methylstyrene and alpha,para-dimethylstyrene. I1 desired, mixturesof the latter three hydrocarbons may also beemployed.

l,2-dicyano-1-rnethylethylene may be prepared by the method of de Wolfand van de Straete, Bull. Sci. Acad. Roy. Belg. 21, 226 (1935).-

Mesaconamide (prepared by ammonolysis of dimethyl mesaconate ormesaconyl chloride) M. P. 175-1'76, was mixed with a slight excess ofP205 and dry distilled. There resulted an 89% yield of1,Z-dicyano-l-methylethylene (mesacononitrile) B. P. 11 15 mm.) 12,,1.4656.

Polymerization of the above-mentioned compounds to form interpolymersmay be carried out by merely heating a mixture of nitrile and the CH2=Csubstituted aromatic hydrocarbon in mass, in solution or in emulsion.The temperature of polymerization may range from 50 C. to 120 0.,although in some cases a higher temperature may be satisfactorilyemployed.

When carrying out a mass polymerization of the above-mentionedingredients, a mixture is first prepared by dissolving the nitrile inthe liquid monomeric CH2=C substituted aromatic hydrocarbon. after whichthe mixture is subjected to polymerizing conditions by the application01. heat either in the absence or in the presence of a polymerizationcatalyst. The latter may be benzoyl peroxide, acetyl peroxide or anyother of the known catalysts of polymerization. For most satisfactoryoperation the mixture should contain from 0.5% to 50% by weight ofdinitrile, although interpolymerization will occur even with greateramounts of dinitrile present, the excess of dinitrile being readilyrecoverable in unpolymerized form.

The amount of l,2rdicyano-l methylethylene combinedas interpolymer may.vary from 1% to by weight of interpolymer, the amount used beingdependent upon the physical characteristics of the interpolymer desired.In general, it may be said that the greater the amount of nitrileemployed, the higher will be the thermal softening point or heatdistortion point.

1,2-dicyano-l-methylethylene is selective in respect to itscopolymerizing properties. It exhibits no tendency to lnterpolymerizewith a great many vinyl compounds such as vinyl chloride, vinyl esterssuch as vinyl acetate or vinyl ethers.

The present interpolymers may be readily obtained in a clear,transparent and chemically stable form. The present products may beemplcyed for the production of transparent objects such as interiayersfor safety glass and the like, for the manufacture of transparent moldedarticles, for electrical insulating materials, etc.

Although the 1,2-dicyano-l-methylethylene does not itself polymerize, Ihave found that in the presence of a CH2=C substituted aromatichydrocarbon it tends to accelerate rather than inhibit thecopolymerizing reaction, i. e., mix-' though, if desired, highertemperatures up to,

say, C. may be employed. However, because of the accelerating effect ofthe dinitrile upon the polymerization reaction, polymerizingtemperatures in the neighborhood of from 50, C. to'80 C. may be usefullyemployed, depending upon the rate of polymerization desired. In general,higher temperatures promote a faster polymerization.

The present interpolymers are characterized by good resistance tochemical reagents, excellent thermal stability and improved resistanceto impact. In general, the copolymerization of styrene with1,2-dicyano-1-methylethylenein the proportion so as to yield from, say,5% to 35% by weight of the copolymerized 1.2-dicyano-1- methylethylenein the interpolymer results in the production of resinous productshaving an impact resistance which is substantially greater than that ofpoly y Because of the selective eflect of the1,2-dicyano-l-methylethylene during its interpolymerization with theCH2=C substituted arcmatic compound, I may employ the polymerizationprocess disclosed in the copending application Reid G. Fordyce, SerialNo. 503,941, filed September 27, 1943, now abandoned, which applicationis assigned to the same assignee as the present application.

For the production of clear, transparent, resinous products derived frommonomeric styrene, I may employ mixtures of monomeric styrene and1,2-dicyano-l-methylethylene, in which mixtures the nitrile content isbelow approximately 50% by weight and preferably below 35% by weight 0!said mixture. During polymerization by mass or solution methods, anddepending upon the relative proportions of the dinitrile and the CH2=Csubstituted aromatic hydrocarbon present in the mixture undergoingpolymerization, one of the constituents thereof will enter the growingpolymer chain at a greater rate than the other constituent. It may,accordingly, be desirable during polymerization to maintain constant theconcentration of the constituent which enters the copolymer at thehighest rate. This may be done as described in the above-mentionedapplication Serial No. 503,941 by a determination of the concentrationof the respective monomers and copolymer present and then adjusting theconcentration of the monomeric mixture to that originally present in themixture.

The polymerization of mixtures of the CH2=C substituted aromatichydrocarbon with the dinitrile, if desired, may be carried tocompletion, 1. e., carried to the stage where a hard, solid, resinousmaterial is obtained which is substantially free from monomericmaterial. Such a method is useful when producing cast objects. For mostpurposes, however, the polymerization is generally carried to a degreewhich is short of complete polymerization and the interpolymerthereafter recovered by solution in a solvent such as benzol or dioxane,which solution is then poured into a lower aliphatic alcohol wherein theinterpolymer is insoluble and in which the unpolymerized monomericmaterials still present are soluble. Such as procedure results in theproduction of a finely divided powdery to fibrous. colorless to slightlyyellowish material which may be washed free of adhering monomericmaterials and solvents and then dried. The material is then suitable foruse as a molding powder.

The invention is further illustrated by means o! the following examples,which are given for the purpose of illustration and are not to beconsidered as limitations upon the present invention.

Example 1 A mixture consisting of 70% by weight of monomeric styrene and30% by weight of 1,2- dicyano-l-methylethylene is made by dissolving thelatter in the styrene and then heating the mixture in the presence 01'1% benzoyl peroxide at 70 C. for 15 days, after which the material isfurther heated at 100 C. for 2 days.

A hard, clear, dark amber, resinous material, soluble in benzene,acetone and dioxane. was obtained. It contained 9% of alcohol solublematerial. The alcohol soluble material was removed from the resinousmaterial by solution in benzene followed by precipitation or thecopolymer in alcohol.

The powdery material thus obtained contained 8.36% nitrogen,corresponding to 27.4% of copolymerized 1,2-dicyano 1 methylethylene. It

may be molded by compression molding in a heated die and was found tohave an ABTM heat distortion point substantially higher than that ofpolystyrene.

In place of styrene, alpha-methylstyrene or alpha, para-dimethylstyrene,or mixtures thereof with styrene, may be employed.

Example 2 A monomeric mixture of styrene and1,2-dicyano-l-methylethylene, said mixture containing approximately 2.5%by weight 0! the dinitrile, is polymerized by heating in the presence ofa polymerization catalyst to a temperature of 50 C. to 60 C. withstirring. During the polymerization, samples of the mixture arewithdrawn and the content of copolymer in the mixture determined byprecipitation in alcohol. The content or the dinitrile in the copolymermay be determined by analysis of its nitrogen content. Based upon theanalysis the amount and composition or the copolymer may be determinedas well as the concentration of the dinitrile in the monomeric mixture.As a result of such an analysis, the amount of interpolymer present, aswell as the composition of the interpolymer and the monomeric mixturecontaining the same, may be evaluated. Based upon such a determinationthe monomeric mixture may be adjusted to that originally present and thecomposition of the copolymer with respect to dinitrile maintained at asubstantially constant value throughout the polymerization.

When polymerizations are carried out as abovedescribed, 1. e., in theabsence of a solvent, the degree of polymerization may be carried to thepoint where the mixture contains between, say,

20% and 30% by weight of the interpolymer.-

At this point the viscosity of the mixture ordinarily becomes too highfor the maintenance of uniformity and the polymerization may beinterrupted and the interpolymer recovered by solution in a solventfollowed by precipitation by addition of a mixture to alcohol.

If desired, the polymerization may be carried out in solution in asolvent such as benzol or dioxane, in which case the polymerization maybe carried to a greater content of copolymer than" was possible in theabsence of a solvent. By the use of suitable amounts of solvents theextent of polymerization may be carried to 60% to 70% of completion.Polymeric material is recovered by precipitation in alcohol. In thismanner a moldable interpolymer which is clear and homogene- Example 3 Amixture comprising '70 g. of styrene, 30 g. oi.1,2-dicyano-l-methylethylene and 30 g. of butyl phthalyl butylglycollate is polymerized by heating at a temperature of C. for 15 daysand then at C. for one day. The resulting hard, clear resin is ground toa powder and then milled on heated rolls. If desired, coloring mattermay Example 4 A mixture consisting of 85 g. of monomeric styrene and g.of 1,2-dicyano-l-methylethylene is emulsified to a fine milk in 120 g.of water containing 3 g. of disodlum phosphate, 0.8 g. of citric acidand 0.04 g. of potassium persulfate and also containing 12.4 g. ofsodium lorol sulfate as an emulsifying agent. The pH of emulsion isabout 5.0. The emulsion is polymerized by refluxing the emulsion(boiling under a reflux condenser for 15 minutes). The emulsion is thenbroken by pouring into methyl alcohol and the precipitated polymer isfiltered, washed with alcohol and water and then dried. Alternativelythe emulsion may be broken by adding a solution of an electrolyte.

The dried, finely divided polymer may then be used directly as a moldingpowder or it may be milled on heated rolls, the sheet thus obtainedcomminuted and employed in hot molding operations.

The herein-described interpolymers are resistant to acids and alkalies,i. e., there is no tendency of the nitrile groups in the interpolymer tohydrolyze. The present products are insoluble in dilute or concentratedacids and dilute or concentrated aqueous alkalies. They are free fromcarboxy groups and also salt groups.

This application is a continuation-in-part of my copending applicationSerial No. 450,514, filed July 11, 1942, now abandoned.

What I claim is:

1. The process which comprises forming a polymerizable mixtureconsisting of a CI-h:C substltuted aromatic hydrocarbon selected fromthe group consisting. of styrene, alpha-methylstyrene andalpha,paradimethylstyrene, together with 1,2dicyano-l-methylethylene,said mixture containing between 0.5% and by weight of said1,2-dicyano-l-methylethylene and then heating said mixture to apolymerizing temperature to form an interpolymer.

2. The process which comprises forming a mixture consisting of styreneand 1,2-dicyano-1- methylethylene, the latter comprising from 0.5% to50% by weight of said mixture and then heating said mixture to apolymerizing temperature to form an interpolymer.

3. A resinous material comprising an interpolymer of styrene and1,2-dicyano-1-methylethylene, said interpolymer containing between 5%and 35% of copolymerized, 1,2-dicyano1- methylethylene, the balancethereof being copolymerized styrene.

4. A resinous material comprising an interpolymer of a CH2=C substitutedaromatic hydrocarbon selected from the group consisting of styrene,alpha-methylstyrene and alpha,paraclimethylstyrene copolymerized with1,2-dicyanol-methylethylene, said interpolymer containing between 1.0%and 50% by weight of copolymerized 1,2-dicyano-1-methylethylene, thebalance of said interpolymer being said CH2=C substituted aromatichydrocarbon.

DAVID T. MOWRY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS France Mar. 8, 1937

